Recently, the importance of development of technologies for reduction of environmental burdens, such as prevention of global warming and conservation of energy resources, has increased rapidly. Among them, technologies to recover and reuse waste heat that has been considered to be useless and discarded are attracting attention.
One of them is an adsorption heat pump. An adsorption heat pump is a technique to convert low-grade thermal energy at 100° C. or lower into useful cold energy by using the transfer of latent heat accompanying the adsorption and desorption of an adsorbate (for example, water or methanol) to and from an adsorbent (for example, silica gel or activated carbon). The temperature at the time of desorption is a relatively low temperature of about 60° C. in some adsorbents. For this reason, as a technology capable of recovering energy from various types of low-temperature waste heat, many researches have been made on adsorption heat pump.
An adsorption heat pump has a condenser and an evaporator. Adsorbate serves as a working medium that transfers heat. After desorbing from adsorbent, adsorbate is cooled in the condenser and undergoes a phase change from vapor to liquid. Liquid adsorbate is sent to the evaporator, which transfers cold energy to the outside. The evaporator generates cold energy by vaporizing liquid adsorbate. The condenser and the evaporator do not necessarily have optimum structure from the viewpoint of efficiency and size. For example, in order to prevent backflow of vapor from the evaporator to the condenser, extra liquid adsorbate is often stored between the evaporator and the condenser so that water blocks the flow path. In order to prevent cold energy from being lost through the flow path, the condenser and the evaporator are often connected by a long tube and disposed at a distance from each other. For these reasons, heat pumps tend to be large. Liquid adsorbate stored in the vicinity of the evaporator in order to pass cold energy to a heat exchanger may bump and spatter under reduced pressure. If spattered drops of water attach to a wall or the like, cold energy is lost and the heat exchange efficiency decreases. Owing to the size of adsorption heat pumps and the difficulty of increasing efficiency, the use of adsorption heat pumps is limited.
The followings are reference documents:    [Document 1] Japanese Laid-open Patent Publication No. 05-272832    [Document 2] Japanese Laid-open Patent Publication No. 2002-100891    [Document 3] Japanese Laid-open Patent Publication No. 05-52446